class A(object):
    # def a(self):
    #     print("A")
    pass


class B(A):
    # def a(self):
    #     print("B")
    pass


class C(A):
    # def a(self):
    #     print("C")
    pass


class D(B, C):
    # def a(self):
    #     print("D")
    pass


# 菱形继承多问题，横向优先
# d = D()
# d.a()
